Purchase this article with an account.
M. D. Roberts, J. Grimm, J. Reynaud, I. A. Sigal, C. F. Burgoyne, J. Downs; Modeling of Optic Nerve Head (ONH) Biomechanics During Acute IOP Elevation: Comparison to Histomorphometric Measures of Connective Tissue Deformation. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2135.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To estimate the scleral and lamina cribrosa (LC) material properties for nonhuman primate (NHP) eyes by comparison of eye-specific finite element (FE) models to serial histologic reconstructions of eye pairs from which acute IOP-related connective tissue deformation was characterized.
3D reconstructions of the ONH were generated for 3 pairs of normal NHP eyes perfusion-fixed at IOP of 10mmHg(OS) and 45mmHg(OD). Connective tissue deformation was characterized using a 3D histomorphometric technique and distilled into two parameters: scleral canal expansion (SCE) and LC displacement (LCD) [IOVS 2009, 50(12)]. Finite element (FE) models of posterior pole were generated for the 10mmHg eyes using an established method [IOVS 2009 August 20, Epub]. Model constants for the scleral and LC elastic moduli were fitted such that the SCE and LCD in the pressurized FE models matched that measured histologically in the contralateral high-IOP eye.
We were able to fit LC and scleral material constants such that the FE model deformations matched both SCE and LCD experimental data well for all three eyes. NHP 3 exhibited a large amount of SCE experimentally, and the models fit to the experimental LCD and SCE data was less precise (8-15% error). Estimated scleral elastic modulus values derived from the model’s fitted parameters (10.4, 7.4, 5.9 MPa) were within the range of previous experimental values for NHP sclera [IOVS 50(11):5226-37]. The LC material constants fell in the range used for previous modeling work.
These results demonstrate that material properties for specimen-specific FE models can be tuned to capture the histologically-measured deformation behavior of ONH connective tissues, thereby providing estimates for the scleral and laminar material properties for an individual eye. Such a fitting technique could provide a powerful means of clinically estimating patient-specific material properties when used in conjunction with emerging technologies like deep-scan SD-OCT.
This PDF is available to Subscribers Only